Poor Metabolizer Phenotype Research Articles

CYP2C19 Poor Metabolizer Status and High System Inflammation Response Index are Independent Risk Factors for Premature Myocardial Infarction: A Hospital-Based Retrospective Study.

Atherosclerosis (AS) is a sustained chronic vascular inflammatory response caused by lipid metabolism disorders and immune response disorders and is the main cause of premature (men ≤ 55 years old, women ≤ 65 years old) myocardial infarction (PMI). Cytochrome P450 2C19 (CYP2C19) (related to vascular function and lipid metabolism) and peripheral immune cell levels and plays an important role in the course of AS. The association CYP2C19 polymorphisms, comprehensive immunoinflammatory indices with PMI susceptibility is unclear. This study included 485 PMI patients, and 639 age-matched non-PMI individuals as controls, from January 2019 to March 2024. The relationship between CYP2C19 polymorphisms, peripheral immunoinflammatory indices (pan-immune inflammation value (PIV), systemic immune inflammation index (SII), and system inflammation response index (SIRI)) and PMI risk were analyzed. The inflammatory indices levels in PMI patients were higher than those in controls (all p<0.05). The frequencies of the CYP2C19 *1/*2 and *2/*2 genotypes were higher, while the frequency of the *1/*1 genotype was lower in the PMI patients than those in controls. The cut-off values of TC, TG, LDL-C, PIV, SII, and SIRI were 5.065, 1.305, 2.805, 410.485, 869.645, and 1.495 for distinguishing PMI, respectively. Logistic regression analysis showed that male (odds ratio (OR): 1.607, 95% confidence interval (CI): 1.134-2.277, p=0.008), history of smoking (OR: 7.108, 95% CI: 4.351-11.614, p<0.001), diabetes mellitus (OR: 4.906, 95% CI: 3.333-7.223, p<0.001), CYP2C19 poor metabolizer (PM) (*2/*2, *2/*3, and *3/*3) (OR: 2.147, 95% CI: 1.279-3.603, p=0.004), and high TG (≥1.305 vs <1.305, OR: 2.598, 95% CI: 1.864-3.623, p<0.001) and SIRI level (≥1.495 vs <1.495, OR: 2.495, 95% CI: 1.432-4.349, p=0.001) were independent risk factors for PMI. CYP2C19 PM phenotype, high SIRI level (≥1.495) and TG level (≥1.305), male, history of smoking, and diabetes mellitus were independently associated with PMI susceptibility.

"CYP3A4 Poor and Intermediate Metabolizers Have a Higher Rate of Steroid-Induced Intraocular Pressure Response".

Evaluate the relationship between CYP3A4 phenotype, the gene encoding the enzyme that metabolizes exogenous steroid, and the rate of steroid-induced intraocular pressure (IOP) response. Lymphocyte-derived DNA sequencing of CYP3A4 from 10073 patients was completed using the PGRN-Seq assay. Subjects with CYP3A4 intermediate metabolizer or slower phenotypes were identified and compared with controls matched by age, race and sex. All subjects had at least three eye exams with at least an exam while on topical/systemic/local steroid in any body location except the eye. Patients with pre-existing glaucoma or glaucoma suspect were excluded. Of the 10073 patients, there were 63 patients who had CYP3A4 poor or intermediate metabolizer phenotype. Of the 63 patients, 22 had documented steroid use. Fifty-nine percent (13/22) of patients with CYP3A4 poor/intermediate metabolizer had a steroid-induced IOP response of 3 mmHg or more, significantly higher compared to 23% (5/22) of matched controls (P=0.031). Although more poor /intermediate metabolizers were steroid responders, the average IOP elevation in steroid responders in both groups were similar (5.0 ± 2.5 mmHg in CYP3A4 poor/intermediate metabolizers compared to 4.1 ± 2.1mmHg in controls, P=0.327). Family history of glaucoma was similar in both groups (7/22 vs. 8/22, P=1.0). Reduced CYP3A4 phenotypes may help identify patients at a higher risk of steroid-induced IOP elevation. This retrospective study examined patients with sequenced CYP3A4, a gene encoding an enzyme that metabolizes exogenous steroids. When compared to normal metabolizers, CYP3A4 poor or intermediate metabolizers have a higher steroid-induced IOP response rate.

CYP2C19 Genotype Is Associated With Adverse Cardiovascular Outcomes in Black Patients Treated With Clopidogrel Undergoing Percutaneous Coronary Intervention.

Cytochrome P450 2C19 (CYP2C19) intermediate and poor metabolizer patients exhibit diminished clopidogrel clinical effectiveness after percutaneous coronary intervention (PCI). However, outcome studies to date have lacked racial diversity. Thus, the impact of CYP2C19 genotype on cardiovascular outcomes in patients treated with clopidogrel who identify as Black or African American remains unclear. Adults among 5 institutions who self-identified as Black or African American, underwent PCI and clinical CYP2C19 genotyping, and were treated with clopidogrel were included. Data were abstracted from health records. Major atherothrombotic (composite of death, myocardial infarction, ischemic stroke, stent thrombosis, or revascularization for unstable angina) and bleeding event rates within 1 year after PCI were compared across CYP2C19 metabolizer groups using multivariable Cox regression adjusted for potential confounders and baseline variables meeting a threshold of P<0.10. The population included 567 Black patients treated with clopidogrel (median age, 62 years; 46% women; 70% with an acute coronary syndrome indication for PCI). Major atherothrombotic events rates were significantly higher among clopidogrel-treated intermediate and poor metabolizers (24 of 125 [19.2%]) versus patients treated with clopidogrel without a no function allele (43 of 442 [9.7%]; 35.1 versus 15.9 events per 100 person-years; adjusted hazard ratio, 2.00 [95% CI, 1.20-3.33], P=0.008). Bleeding event rates were low overall (23 of 567 [4.1%]) and did not differ among the metabolizer groups. Black patients with CYP2C19 intermediate and poor metabolizer phenotypes who are treated with clopidogrel exhibit increased risk of adverse cardiovascular outcomes after PCI in a real-world clinical setting. Bleeding outcomes should be interpreted cautiously. Prospective studies are needed to determine whether genotype-guided use of prasugrel or ticagrelor in intermediate and poor metabolizers improves outcomes in Black patients undergoing PCI.

Impact of CYP2C19 Gene Variants on Long-Term Treatment with Atorvastatin in Patients with Acute Coronary Syndromes.

The effectiveness of lipid-lowering therapies may be insufficient in high-risk cardiovascular patients and depends on the genetic variability of drug-metabolizing enzymes. Customizing statin therapy, including treatment with atorvastatin, may improve clinical outcomes. Currently, there is a lack of guidelines allowing the prediction of the therapeutic efficacy of lipid-lowering statin therapy. This study aimed to determine the effects of clinically significant gene variants of CYP2C19 on atorvastatin therapy in patients with acute coronary syndromes. In total, 92 patients with a confirmed diagnosis of ST-elevation myocardial infarction (STEMI) or non-ST-elevation myocardial infarction (NSTEMI) were sequenced for target regions within the CYP2C19 gene on the Illumina Miniseq system. The CYP2C19 poor metabolizer phenotype (carriers of CYP2C19*2, CYP2C19*4, and CYP2C19*8 alleles) was detected in 29% of patients. These patients had significantly lower responses to treatment with atorvastatin than patients with the normal metabolizer phenotype. CYP2C19-metabolizing phenotype, patient age, and smoking increased the odds of undertreatment in patients (∆LDL-C (mmol/L) < 1). These results revealed that the CYP2C19 phenotype may significantly impact atorvastatin therapy personalization in patients requiring LDL lipid-lowering therapy.

Is CYP2C Haplotype Relevant for Efficacy and Bleeding Risk in Clopidogrel-Treated Patients?

A recently discovered haplotype-CYP2C:TG-determines the ultrarapid metabolism of several CYP2C19 substrates. The platelet inhibitor clopidogrel requires CYP2C19-mediated activation: the risk of ischemic events is increased in patients with a poor (PM) or intermediate (IM) CYP2C19 metabolizer phenotype (vs. normal, NM; rapid, RM; or ultrarapid, UM). We investigated whether the CYP2C:TG haplotype affected efficacy/bleeding risk in clopidogrel-treated patients. Adults (n = 283) treated with clopidogrel over 3-6 months were classified by CYP2C19 phenotype based on the CYP2C19*2*17 genotype, and based on the CYP2C19/CYP2C cluster genotype, and regarding carriage of the CYP2:TG haplotype, and were balanced on a number of covariates across the levels of phenotypes/haplotype carriage. Overall, 45 (15.9%) patients experienced ischemic events, and 49 (17.3%) experienced bleedings. By either classification, the incidence of ischemic events was similarly numerically higher in PM/IM patients (21.6%, 21.8%, respectively) than in mutually similar NM, RM, and UM patients (13.2-14.8%), whereas the incidence of bleeding events was numerically lower (13.1% vs. 16.6-20.5%). The incidence of ischemic events was similar in CYP2C:TG carries and non-carries (14.1% vs. 16.1%), whereas the incidence of bleedings appeared mildly lower in the former (14.9% vs. 20.1%). We observed no signal to suggest a major effect of the CYP2C19/CYP2C cluster genotype or CYP2C:TG haplotype on the clinical efficacy/safety of clopidogrel.

Effect of CYP2D6 genetic variation on patient-reported symptom improvement and side effects among children and adolescents treated with amphetamines.

Amphetamine-based medications are recommended as a first-line pharmacotherapy for the treatment of attention-deficit/hyperactivity disorder in children and adolescents. However, the efficacy and tolerability of these medications vary across individuals, which could be related to interindividual differences in amphetamine metabolism. This study examined if genotype-predicted phenotypes of the cytochrome P450 isozyme CYP2D6 were associated with self-reported side effects and symptom improvement in youth treated with amphetamines. Two hundred fourteen participants aged 6-24 who had a history of past or current amphetamine treatment were enrolled from Western Canada. Amphetamine dose and duration information was collected from the participants along with questions regarding adherence, concomitant medications, symptom improvement and side effects. DNA was extracted from saliva samples and genotyped for CYP2D6 . Binomial logistic regression models were used to determine the effect of CYP2D6 metabolizer phenotype with and without correction for phenoconversion on self-reported symptom improvement and side effects. Genotype-predicted CYP2D6 poor metabolizers had significantly higher odds of reporting symptom improvement when compared to intermediate metabolizers (OR = 3.67, 95% CI = 1.15-11.7, P = 0.029) after correction for phenoconversion and adjusting for sex, age, dose, duration, and adherence. There was no association between CYP2D6 metabolizer phenotype and self-reported side effects. Our findings indicate that phenoconverted and genotype-predicted CYP2D6 poor metabolizer phenotype is significantly associated with higher odds of symptom improvement in children and adolescents treated with amphetamine. If replicated, these results could inform the development of future dosing guidelines for amphetamine treatment in children and adolescents.

Precision dosing of venlafaxine during pregnancy: a pharmacokinetics modelling approach.

Venlafaxine exposure through gestation is affected by the longitudinal changes in maternal physiology. Confounding treatment is also the impact of CYP2D6 polymorphisms affecting plasma concentrations of venlafaxine. A pharmacokinetic modelling approach was employed to assess variations in maternal and foetal cord venlafaxine levels throughout gestation and to identify appropriate doses to maintain venlafaxine levels within the therapeutic range. Throughout gestation, there was a significant decrease in simulated venlafaxine trough plasma concentrations in both extensive metaboliser (EM) and ultra-rapid metaboliser (UM) phenotypes. Approximately 70%-87% of EM and UM phenotypes exhibited trough venlafaxine plasma concentrations below the therapeutic level (<25 ng/ml), which increased to 96% at week 30. While for poor metabolizer (PM) phenotypes, the percentage was approximately 4%. The standard daily dose of 75 mg required adjustment for all phenotypes examined during gestation. A daily dose of 37.5-112.5 mg is appropriate for PM throughout pregnancy. For EM, a dose of 225 mg daily in the first trimester, 262.5 mg daily in the second trimester, and 375 mg daily in the third trimester is suggested to be optimal. For UM, a dose of 375 mg daily throughout gestation is suggested to be optimal.

Retrospective pharmacogenetic study in a cohort of pediatric tuberous sclerosis complex patients using everolimus.

Aim: Tuberous sclerosis complex (TSC) is a rare disease that produces multisystemic disorders. Everolimus (EVR) is the only immunosuppressive drug approved to control the symptoms and progression of the disease. The aim was to evaluate the genotype-phenotype association to improve the pediatric TSC pharmacotherapeutic outcome. Patients & methods: Ten pediatric TSC patients were recruited. Concomitant treatment and main metabolic enzymes and transporter coding gene variants of EVR were analyzed. Results: Significant associations were found between CYP3A4*22 allele and concomitant treatment with valproic acid (CYP3A4-inhibitor) with a poor metabolizer phenotype and the presence of pneumonia. Conclusion: This is the first pharmacogenetic study of EVR in pediatric TSC patients. The authors propose to consider concomitant treatment and pharmacogenetics due to their multifactorial status.

Severe systemic adverse reactions to ophthalmic timolol in a CYP2D6 homozygous *4 allele carrier: a case report.

A woman with ocular hypertension suffered from severe bradycardia, hypotensionand syncope attacks in temporal relation with ophthalmic timolol application. Topically applied timolol is nasally absorbed and has been shown to reach potentially relevant systemic concentrations. Timolol is mainly metabolized by CYP2D6, which exhibits interindividual metabolic capacity due to genetic variations. A reactive pharmacogeneticpanel test identified the patient as a CYP2D6 homozygous *4 allele carrier, which has been associated with a poor metabolizerphenotype and lacking enzyme activity. Thus, the adverse drug reactions possibly resulted from increased systemic timolol exposure. This case report highlights that pharmacogenetic panel testing can contribute to safe and effective pharmacotherapy, even for topically applied drugs.

Cytochrome P450 2B6 6 distribution among Burkinabè population

Mutations affect the genes that encode certain cytochromes P450 (CYP450) isoenzymes that are responsible for metabolism of drugs. The aim of this study was to determine the frequency of CYP2B6 (516G&gt;T) SNP in the Burkinabè population. Genomic DNA extraction from blood was performed by GenJET® Genomic DNA according to the manufacturer’s instructions. Genotyping for the cytochrome P450 variant alleles was performed using predesigned primers. The amplification was carried out by PCR while the differentiation between the alleles was carried out after digestion with restriction enzymes by electrophoresis. The CYP2B6 c.516G&gt;T was successfully analyzed in 92,38% (291/315) of the study participants. Among the investigated individuals, the distribution of the major allele CYP2B6*G was 56% and the minor CYP2B6*T allele was 44%. The results obtained showed a prevalence of 56% for the G allele and 44% for the T allele. This was distributed as 31% for the GG genotype (reduced dosage required), 51% for the GT genotype (normal dosage range), and 18% for the TT genotype (high drug toxicity). The presence of the rapid and poor metabolizer phenotypes in the studied sample shows the need for additional studies to better assess their impact on Burkinabe people.

The impact of CYP2C19 genotype on phenoconversion by concomitant medication

Introduction: Pharmacogenetics-informed drug prescribing is increasingly applied in clinical practice. Typically, drug metabolizing phenotypes are determined based on genetic test results, whereupon dosage or drugs are adjusted. Drug-drug-interactions (DDIs) caused by concomitant medication can however cause mismatches between predicted and observed phenotypes (phenoconversion). Here we investigated the impact of CYP2C19 genotype on the outcome of CYP2C19-dependent DDIs in human liver microsomes.Methods: Liver samples from 40 patients were included, and genotyped for CYP2C19*2, *3 and *17 variants. S-mephenytoin metabolism in microsomal fractions was used as proxy for CYP2C19 activity, and concordance between genotype-predicted and observed CYP2C19 phenotype was examined. Individual microsomes were subsequently co-exposed to fluvoxamine, voriconazole, omeprazole or pantoprazole to simulate DDIs.Results: Maximal CYP2C19 activity (Vmax) in genotype-predicted intermediate metabolizers (IMs; *1/*2 or *2/*17), rapid metabolizers (RMs; *1/*17) and ultrarapid metabolizers (UMs; *17/*17) was not different from Vmax of predicted normal metabolizers (NMs; *1/*1). Conversely, CYP2C19*2/*2 genotyped-donors exhibited Vmax rates ∼9% of NMs, confirming the genotype-predicted poor metabolizer (PM) phenotype. Categorizing CYP2C19 activity, we found a 40% concordance between genetically-predicted CYP2C19 phenotypes and measured phenotypes, indicating substantial phenoconversion. Eight patients (20%) exhibited CYP2C19 IM/PM phenotypes that were not predicted by their CYP2C19 genotype, of which six could be linked to the presence of diabetes or liver disease. In subsequent DDI experiments, CYP2C19 activity was inhibited by omeprazole (−37% ± 8%), voriconazole (−59% ± 4%) and fluvoxamine (−85% ± 2%), but not by pantoprazole (−2 ± 4%). The strength of CYP2C19 inhibitors remained unaffected by CYP2C19 genotype, as similar percental declines in CYP2C19 activity and comparable metabolism-dependent inhibitory constants (Kinact/KI) of omeprazole were observed between CYP2C19 genotypes. However, the consequences of CYP2C19 inhibitor-mediated phenoconversion were different between CYP2C19 genotypes. In example, voriconazole converted 50% of *1/*1 donors to a IM/PM phenotype, but only 14% of *1/*17 donors. Fluvoxamine converted all donors to phenotypic IMs/PMs, but *1/*17 (14%) were less likely to become PMs than *1/*1 (50%) or *1/*2 and *2/*17 (57%).Conclusion: This study suggests that the differential outcome of CYP2C19-mediated DDIs between genotypes are primarily dictated by basal CYP2C19 activity, that may in part be predicted by CYP2C19 genotype but likely also depends on disease-related factors.

Trial of a Novel Oral Cannabinoid Formulation in Patients with Hypertension: A Double-Blind, Placebo-Controlled Pharmacogenetic Study.

Cannabidiol (CBD) is a non-psychoactive cannabinoid, and available evidence suggests potential efficacy in the treatment of many disorders. DehydraTECH™2.0 CBD is a patented capsule formulation that improves the bioabsorption of CBD. We sought to compare the effects of CBD and DehydraTECH™2.0 CBD based on polymorphisms in CYP P450 genes and investigate the effects of a single CBD dose on blood pressure. In a randomized and double-blinded order, 12 females and 12 males with reported hypertension were given either placebo capsules or DehydraTECH™2.0 CBD (300 mg of CBD, each). Blood pressure and heart rate were measured during 3 h, and blood and urine samples were collected. In the first 20 min following the dose, there was a greater reduction in diastolic blood pressure (p = 0.025) and mean arterial pressure MAP (p = 0.056) with DehydraTECH™2.0 CBD, which was probably due to its greater CBD bioavailability. In the CYP2C9*2*3 enzyme, subjects with the poor metabolizer (PM) phenotype had higher plasma CBD concentrations. Both CYP2C19*2 (p = 0.037) and CYP2C19*17 (p = 0.022) were negatively associated with urinary CBD levels (beta = -0.489 for CYP2C19*2 and beta = -0.494 for CYP2C19*17). Further research is required to establish the impact of CYP P450 enzymes and the identification of metabolizer phenotype for the optimization of CBD formulations.

Study protocol of the HD-MED study aiming to personalize drug treatment in Huntington's disease: a longitudinal, observational study to assess medication use and efficacy in relation to pharmacogenetics.

Huntington's disease (HD) is a hereditary, neurodegenerative disorder characterized by motor, cognitive, and psychiatric symptoms. Currently, HD can only be managed symptomatically, including a large variety of prescribed drugs. Many HD patients experience negative medication effects (e.g. side effects or non-response). Pharmacogenetic (PGx) studies show how genetic variation affects both medication efficacy and toxicity and holds the potential to improve these outcomes of drug treatment. To classify the effect of the PGx profile of CYP2C19 and CYP2D6 in HD gene expansion carriers on negative medication effects of HD-related medication. Multicenter, observational study with 1-year follow-up. Adult HD gene expansion carriers who use one or more HD-related medications are eligible to participate. A detailed overview of medication use, medication efficacy, and side effects is retrospectively and prospectively collected via medication diaries, questionnaires, phone calls, and pharmacy medication verification schemes. PGx analysis on whole blood-extracted DNA is performed with Agena Bioscience VeriDose® Core Panel and long-range polymerase chain reaction copy number variation analysis. Per the study protocol-defined negative medication effects in HD gene expansion carriers with a genotype predicted poor or ultrarapid metabolizer phenotype will be compared with HD gene expansion carriers with a predicted intermediate and normal metabolizer phenotype. Frequencies will be analyzed via χ2 and logistic multivariate regression analysis. In addition, we summarize in this manuscript HD-relevant PGx prescription recommendations to improve drug therapy. The original study protocol was approved by the medical research ethics committee Leiden Den Haag Delft on 26 November 2019. HD-MED is a low-risk study that will generate personalized PGx results that can immediately be implemented in clinical practice, thus potentially improving pharmacovigilance and patients' quality of life. This study is registered in the International Clinical Trial Registry Platform under registration number NL8251, URL https://trialsearch.who.int/Trial2.aspx?TrialID=NL8251.

Identification of Escitalopram Metabolic Ratios as Potential Biomarkers for Predicting CYP2C19 Poor Metabolizers.

Escitalopram is metabolized by CYP2C19 to N-desmethyl escitalopram and escitalopram propionic acid. The primary aims of this study were to investigate the impact of the CYP2C19 phenotype on metabolic ratios of escitalopram in vivo and propose a biomarker for the CYP2C19 phenotype in patients treated with escitalopram. Median steady-state serum metabolite/parent drug ratio of N-desmethyl escitalopram and escitalopram propionic acid was investigated across CYP2C19 genotype-translated phenotype groups. The receiver operator characteristics method and the area-under-the-receiver-operator-characteristics curve was used to determine the best suited metabolic ratio for detecting CYP2C19 poor metabolizers (PMs). A total of 441 patients were included in the study. The N-desmethyl escitalopram/escitalopram ratio was 67% and 44% lower in CYP2C19 PMs and intermediate metabolizers (IMs), respectively, than normal metabolizers. Furthermore, the ability of the ratio to predict CYP2C19 PMs was 92%. A metabolic ratio of <0.24 was detected in 8 of 8 PMs in the study, indicating that it is a promising biomarker of reduced CYP2C19 activity. The escitalopram propionic acid/escitalopram ratio was 77% and 48% lower in CYP2C19 PMs and IMs, respectively; however, the ability of the ratio to detect CYP2C19 PMs was only 87%. These findings suggest that DECT/ECT reflects CYP2C19 activity, and a metabolic ratio of <0.24 strongly predicts CYP2C19 PM phenotype. The ratio could be a valuable alternative to genotyping in personalized dosing of escitalopram and possibly other CYP2C19 substrates. The escitalopram propionic acid/escitalopram ratio was also associated with CYP2C19 activity; however, the ratio was inferior to the DECT/ECT at predicting PMs.

Explore the distribution of (rs35742686, rs3892097 and rs1065852) genetic polymorphisms of cytochrome P4502D6 gene in the Moroccan population

BackgroundThe CYP2D6 gene encodes a crucial enzyme involved in the metabolic pathways of many commonly used drugs. It is a highly polymorphic gene inducing an interethnic and interindividual variability in disease susceptibility and treatment response. The aim of this study is to evaluate the frequency of the three CYP2D6 most investigated alleles (CYP2D6*3, CYP2D6*4, and CYP2D6*10 alleles) in Morocco compared to other populations.This study enrolled 321 healthy Moroccan subjects. CYP2D6 genotypes and allele frequencies were assessed using a restriction fragment length polymorphism–polymerase chain reaction genotyping method. The Principal Component Analysis (PCA) and dendrogram were conducted to evaluate genetic proximity between Moroccans and other populations depending on CYP2D6 allele frequencies.ResultsAccording to the current study, the results observed the homozygous wild type of the three studied SNPs were predominant among the Moroccan population, while 1.4% of Moroccans carried the CYP2D6*4 allele responsible for a Poor Metabolizer phenotype and associated with low enzyme activity which may induce a treatment failure. The PCA and cluster dendrogram tools revealed genetic proximity between Moroccans and Mediterranean, European and African populations, versus a distancing from Asian populations.ConclusionThe distribution of CYP2D6 polymorphisms within Morocco follows the patterns generally found among the Mediterranean, European and African populations. Furthermore, these results will help to lay a basis for clinical studies, aimed to introduce and optimize a personalized therapy in the Moroccan population.

The Impact of Pharmacogenomic CYP3A5 Variants on Calcineurin Inhibitor Metabolism and SLCO1B1 Variants on Methotrexate in Adult Allogeneic BMT Patients

Allogeneic blood and marrow transplant (BMT) is used to transplant a new immune system in patients with hematologic malignancies or immune-mediated disease. BMT patients require initial immune suppression to prevent graft rejection and graft versus host disease (GVHD). Tacrolimus and cyclosporine are calcineurin inhibitors (CNI) and methotrexate is an antimetabolite used to mitigate this immune response. Tacrolimus has data supporting oral dose variation based on pharmacogenomic (PGx) studies for Intermediate Metabolizers (IM) and Poor Metabolizers (PM) on studies done in kidney transplant patients. There are fewer studies on BMT patients in this field, and even less on the variability of IV to oral conversion dosing and first pass metabolism effect based on PGx profiles. Methotrexate has been shown to have PGx mutations affecting its metabolism at higher dosing used for chemotherapy, but its impact on BMT patient dosing is not well-defined. Based on our study, we found statistically significant variability in Tacrolimus concentration based on drug assay levels compared with dosing for Intravenous (IV) and oral formulation based on PGx predicted phenotypes. We further noted a profound effect on first pass metabolism when transitioning between IV and oral dosing of Tacrolimus based on PGx predicted phenotypes. The average oral dose in predicted IM phenotypes divided by the IV dose was 2.68. For the predicted PM phenotype, the average oral dose divided by the IV dose was 1.18. The p-value in a two-tailed nonparametric T-test with equal variance assessing the conversion factor from IV to oral dosing in predicted IM versus PM phenotypes was significant with a p-value of 0.002. Methotrexate metabolism did not seem to be affected by PGx mutations at the doses used for BMT GVHD prevention.

Pharmacological counseling in hepatotoxicity induced by macitentan and selexipag: a case report

BackgroundPulmonary arterial hypertension is a progressive, debilitating condition characterized by increased resistance in the pulmonary arterial circulation. Current treatments for pulmonary arterial hypertension include endothelin receptor antagonists such as bosentan, sitaxentan, ambrisentan, macitentan, and oral prostacyclin receptor agonists such as selexipag. Endothelin receptor antagonists have been associated with liver injury, while hepatotoxicity was not reported for selexipag. Although genetic variability has been indisputably associated with variability in drug response, no study has been designed until now to assess its effects on the pharmacokinetics of endothelin receptor antagonists or selexipag.Case presentationWe report the case of a 58-year-old female Caucasian patient with a dramatic increase in plasma levels of transaminases after treatment with macitentan and selexipag, drugs whose risk of causing liver injury has so far been considered limited. After therapy discontinuation, plasma levels of transaminases returned to baseline, thus suggesting a role of these drugs in the observed hepatotoxicity. After pharmacological counseling, we decided to introduce ambrisentan for the patient’s treatment. After 7 months of treatment, no liver injury has been reported. To evaluate the role of genetic factors in the observed hepatotoxicity, we genotyped the patient for single-nucleotide polymorphisms previously associated with macitentan, ambrisentan, or selexipag metabolism. We found a genetic profile associated with a poor metabolizer (PM) phenotype for CYP2C8 and CYP2C9, key enzymes for elimination of both macitentan and selexipag. The reported results suggest that an allelic profile associated with low activity for CYP2C8 and CYP2C9 enzyme could be a potential risk factor for macitentan and selexipag-induced liver injury and could provide a possible marker for early identification of subjects at higher risk of developing hepatotoxicity.ConclusionsA multidisciplinary approach based on clinical evaluation, as well as pharmacological counseling and evaluation of the patient’s genetic profile, might be useful for identification of patients with a high chance of drug-induced liver injury, avoiding unnecessary risks in therapy selection and prescription.

Physiologically-Based Pharmacokinetic Model Development, Validation, and Application for Prediction of Eliglustat Drug-Drug Interactions.

Eliglustat is a glucosylceramide synthase inhibitor indicated as a long-term substrate reduction therapy for adults with type 1 Gaucher disease, a lysosomal rare disease. It is primarily metabolized by cytochrome P450 2D6 (CYP2D6), and variants in the gene encoding this enzyme are important determinants of eliglustat pharmacokinetics (PK) and drug-drug interactions (DDIs). The existing drug label addresses the DDIs to some extent but has omitted scenarios where both metabolizing CYPs (2D6 and 3A4) are mildly or moderately inhibited. The objectives of this study were (i) to develop and validate an eliglustat physiologically-based pharmacokinetic (PBPK) model with and without drug interactions, (ii) to simulate untested DDI scenarios, and (iii) to explore potential dosing flexibility using lower dose strength of eliglustat (commercially not available). PK data from healthy adults receiving eliglustat with or without interacting drugs were obtained from literature and used for the PBPK model development and validation. The model-predicted single-dose and steady-state maximum concentration (Cmax ) and area under the concentration-time curve (AUC) of eliglustat were within 50-150% of the observed values when eliglustat was administered alone or coadministered with ketoconazole or paroxetine. Then as model-based simulations, we illustrated eliglustat exposure as a victim of interaction when coadministered with fluvoxamine following the US Food and Drug Administration (FDA) dosing recommendations. Second, we showed that with lower eliglustat doses (21 mg, 42 mg once daily) the exposure in participants of intermediate and poor metabolizer phenotypes was within the outlined safety margin (Cmax <250 ng/mL) when eliglustat was administered with ketoconazole, where the current recommendation is a contraindication of coadministration (84 mg). The present study demonstrated that patients with CYP2D6 deficiency may benefit from lower doses of eliglustat.

Impact of cytochrome P450 2D6 polymorphisms on decision-making and clinical outcomes in adjuvant hormonal therapy for breast cancer

BACKGROUNDThere are concerns that tamoxifen is less effective in Asian women because of the high prevalence of impaired function cytochrome P450 2D6 (CYP2D6) polymor-phisms.AIMTo evaluate how knowledge of CYP2D6 genotype impacted the choice of hormonal agent and how CYP2D6 genotype and agent were associated with clinical outcomes.METHODSEighty-two women were recruited. Seventy-eight completed CYP2D6 genotyping and were categorized into poor, intermediate (IM) and extensive or ultra metabolizer phenotypes. Women with poor metabolizer and IM phenotypes were recommended aromatase inhibitors as the preferred agent.RESULTSMore than 70% of the women had an IM phenotype, 32% an extensive or ultra metabolizer phenotype, and 0% had a poor metabolizer phenotype. Regardless of genotype, more women opted for aromatase inhibitors. Overall, 80% of women completed 5 years of hormonal therapy. Five women developed recurrence, 3 contralateral breast cancer, 5 died, and 1 was diagnosed with a second primary cancer. Five-year recurrence-free and overall survival were slightly better in women with the extensive or ultra metabolizer phenotype compared to those with the IM phenotype, though not statistically significant [P = 0.743, hazard ratio (HR): 1.441, 95% confidence interval (CI): 0.191 to 10.17 and P = 0.798, HR: 1.327, 95%CI: 0.172 to 9.915, respectively]. Women receiving aromatase inhibitors also appeared to have a better, but also nonsignificant, 5-year recurrence-free and overall survival (P = 0.253, HR: 0.368, 95%CI: 0.031 to 0.258 and P = 0.292, HR: 0.252, 95%CI: 0.005 to 4.951, respectively).CONCLUSIONThe IM phenotype was highly prevalent but was not associated with clinical outcome.

Therapeutic drug monitoring and CYP2C19 genotyping guide the application of voriconazole in children

BackgroundThis study used therapeutic drug monitoring (TDM) and CYP2C19 gene polymorphism analysis to explore the efficacy and safety of different doses of voriconazole (VCZ) for the clinical treatment of pediatric patients, with the aim of providing guidelines for individualized antifungal therapy in children.MethodsOur study enrolled 94 children with 253 VCZ concentrations. The genotyping of CYP2C19 was performed by polymerase chain reaction (PCR)-pyrosequencing. VCZ trough concentration (Ctrough) was detected by high-performance liquid chromatography-tandem mass spectrometry. SPSS 23.0 was used to analyze the correlations between VCZ concentration, CYP2C19 phenotype, adverse effects (AEs), and drug-drug interactions.ResultsA total of 94 children aged between 1 and 18 years (median age 6 years) were enrolled in the study. In total, 42.6% of patients reached the therapeutic range at initial dosing, while the remaining patients reached the therapeutic range after the adjustment of the dose or dosing interval. CYP2C19 gene polymorphism was performed in 59 patients. Among these patients, 24 (40.7%) had the normal metabolizer (NM) phenotype, 26 (44.1%) had the intermediate metabolizer (IM) phenotype, and 9 (15.3%) had the poor metabolizer (PM) phenotype. No cases of the rapid metabolizer (RM) or ultrarapid metabolizer (UM) phenotypes were found. The initial VCZ Ctrough was significantly higher in patients with the PM and IM phenotypes than in those with the NM phenotype. The combination of immunosuppressive drugs (ISDs) did not affect VCZ Ctrough. The incidence of AEs was 25.5%, and liver function damage (46.2%) and gastrointestinal reactions (19.2%) were the most common.ConclusionsOur study showed significant individual differences of VCZ metabolism in children. Combining TDM with CYP2C19 gene polymorphism has important guiding significance for individualized antifungal therapy in pediatric patients.